Display adapter WDDM 1.0

I want to upgrade three Dell Inspiron 530S workstations from XP to Windows 8.1. The requirements say the display adapter must be
DirectX 9 graphics device with WDDM 1.0 or higher drive.
I confirmed DirectX9 using the dxdiag program, but I'm not sure about the WDDM driver.
Anyone know how I can confirm WDDM 1.0 on the display adapter?